Cable ties are well known devices used to bundle or secure a group of articles such as electrical wires or cables. U.S. Pat. No. 3,102,311 is an early example of ties used for such purposes.
Cable ties of conventional construction include a cable tie head, a longitudinal strap extending from the head and a tail at the opposite end of the strap. The strap is wrapped around a bundle of articles and the tail is inserted through an aperture or passage in the head. The head of the cable tie typically supports a locking element which extends into the head passage and which is engagable with the body of the strap upon insertion into the head passage so that when the tail is pulled through the head passage, the locking element secures the strap body in the head.
Advances in cable tie construction have taken many forms and shapes. Many of these advances have been in the area of the locking element carried in the cable tie head to secure the strap therein.
The art has seen the use of flexible locking elements which are integrally molded with the head. One example of such a tie is U.S. Pat. No. 3,965,538. Also, ties have been developed employing metallic barbs embedded into the head which serve as the locking element. One example of a metallic barb tie is U.S. Pat. No. 3,186,047.
The metallic barb cable ties have been long known to exhibit exceptional pull-out performance in that the barb securely bites into the strap locking the strap in place in the head. Such metallic barb ties include the barb being embedded into the cable tie head at an acute angle with respect to the inserted tail. An end of the barb extends into the head passage and engages the strap upon insertion thereinto. Due in part to the bending characteristics of the barb as well as the angle at which it is embedded, the metal barb permits insertion of the cable tie strap through the head aperture. Upon an attempt to withdraw the strap in a direction opposite the insertion direction, the barb end bites into the strap, preventing such withdrawal. In addition to the '047 patent, other examples of cable ties having such construction are shown and described in U.S. Pat. Nos. 3,488,813 and 3,457,598.
As the metal barb of the cable tie actually bites into the inserted strap body in order to prevent withdrawal, cable ties of this type of construction exhibit high long-term pull-out resistance. This results in the cable tie having good tensile strength when coiled around a bundle (loop tensile strength) after aging. This is an important criteria in the selection and use of cable ties. However one perceived disadvantage of metallic barb cable ties is that the tie exhibits relatively high strap insertion forces. As the metallic barb must be deflected to permit insertion of the strap, the force necessary to deflect the barb must be overcome. This force can be even more significant in larger sized cable ties.
The cable tie art has seen attempts to construct cable ties which would have the pull-out strength of a cable tie having an embedded metallic barb while still exhibiting low insertion force. One such attempt is a multiple piece cable tie such as shown in U.S. Pat. No. 5,121,524 where the cable tie is formed to have a head including a hingedly mounted pawl which holds a metallic barb therein. The pawl is flexibly rotatably movable within the head upon insertion of the strap. The metal barb supported by the pawl bites into the strap upon attempted withdrawal of the strap. A further example is also shown in U.S. Pat. No. 5,193,251 where the head of the cable tie includes a metallic barb supported on a cantilevered platform. The platform is deflectable upon insertion of the strap through the aperture to permit ease of passage therethrough. The barb is positioned for biting insertion into the strap upon an attempt to withdraw the strap from the aperture. While the cable ties shown in each of these patents provide, to some degree, the above noted features, such multi-component ties are more difficult to manufacture as the tie head must form a flexible pawl or platform which must securely retain the barb.
A still further attempt to decrease the insertion force necessary to insert the strap into the cable tie head is to embed the barb into the plastic of the head at a high angle. Cable ties of this design are manufactured by the assignee herein as well as by Panduit Corp. However, it has been found that this type of tie is difficult to construct as barb support at such an angle may be difficult to economically manufacture.
There thus still exists a need to provide a cable tie which exhibits high long-term loop tensile strength as well as low strap insertion force and which may be manufactured in an economical fashion.